The Collaborative International Dictionary
Obtenebration
Obtenebration \Ob*ten`e*bra"tion\, n. [L. obtenebrate to make dark.] The act of darkening; the state of being darkened; darkness.
In every megrim or vertigo, there is an obtenebration
joined with a semblance of turning round.
--Bacon.
Wiktionary
obtenebration
n. (context obsolete English) The act of darkening; darkness.